The subject matter of this disclosure relates generally to processing of botanical matter to extract some components found therein while avoiding extraction of other components that may be found therein. A variety of useful therapeutic and non-therapeutic substances are found in different types of botanical matter. For example, willow trees produce salicylic acid which is the active metabolite of aspirin. Other examples include ginseng, goldenseal, digitalis, cascara, wormseed and hemp. Cannabis, which has more recently become recognized for its medicinal properties, contains substances which have therapeutic value for patients with chronic pain, multiple sclerosis, epilepsy and HIV/Aids. Botanical matter may also contain undesirable substances, e.g. natural toxins, heavy metals, or pesticides. Removal of the undesirable substances may increase the value or safety of the botanical matter. Further, extraction of useful substances while avoiding extraction of undesirable substances may help to avoid further processing for purification purposes.
It is known to extract substances from botanical matter using a solvent. For example, dried and milled botanical matter may be mixed with the solvent for some period of time and then physically separated from the botanical matter solids to produce an extracted solution and a residue. Depending upon the intended application for the soluble components and the properties of the solvent, extracts may be used directly, mixed with other components, or the soluble components may be separated from the solvent to produce a concentrate. In order to facilitate separation of the targeted substance from the solvent, the solvent may be selected such that it is a liquid or fluid under the temperature and pressure conditions of the extraction process, and either the solvent or the substance (but not both) is a gas under the temperature and pressure conditions of the separation process. It is also known to effect a liquid phase separation through the addition of a miscible non-solvent or a salt that reduces the solubility of the targeted substance in the solvent. In either case, an efficient extraction is characterized by a rapid and complete dissolution in a small volume of solvent (as concentrated as possible), and a quantitative separation of the extract solution from the residue that may contain plant fibers, waxes, lipids, and liquids that are not dissolved in the solvent. Inefficient extractions take a long time, incompletely dissolve the components of interest (partial extraction), use large solvent volumes (thereby transferring more poorly soluble non-target components), fail to recover all the solvent from the residue, e.g. hand squeezing solvent soaked botanical material through cheese cloth, and transport botanical components via non-solubility mediated mechanism, e.g. plant fragments passing through a course screen or insoluble components (water) ending up in the collection vessel of conventional supercritical CO2 processes.